This application shows an double sheet detection example on a rollforming machine. On this machine the sheet infeed is protected against double sheets by 2 dual- head sensors, fixed opposit each other. Each sheet passes between the both sensors and protect so the forming rolls against demages by double sheets.The contact of the double sheet detector amplifier switches off the sheet feed as soon as double sheets pass the sensors. This contact is also used to activate optical and acoustical alarms to call the machine operator.